EP0164725B1 - Perpendicular magnetization film and its production - Google Patents
Perpendicular magnetization film and its production Download PDFInfo
- Publication number
- EP0164725B1 EP0164725B1 EP85107164A EP85107164A EP0164725B1 EP 0164725 B1 EP0164725 B1 EP 0164725B1 EP 85107164 A EP85107164 A EP 85107164A EP 85107164 A EP85107164 A EP 85107164A EP 0164725 B1 EP0164725 B1 EP 0164725B1
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- European Patent Office
- Prior art keywords
- film
- bismuth
- samarium
- magnetic
- cobalt
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- 238000004519 manufacturing process Methods 0.000 title claims 2
- 239000010408 film Substances 0.000 claims description 56
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 claims description 41
- 229910052797 bismuth Inorganic materials 0.000 claims description 36
- 239000000758 substrate Substances 0.000 claims description 30
- 239000010941 cobalt Substances 0.000 claims description 27
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 27
- 239000010409 thin film Substances 0.000 claims description 22
- KZUNJOHGWZRPMI-UHFFFAOYSA-N samarium atom Chemical compound [Sm] KZUNJOHGWZRPMI-UHFFFAOYSA-N 0.000 claims description 21
- 229910052772 Samarium Inorganic materials 0.000 claims description 20
- 229910017052 cobalt Inorganic materials 0.000 claims description 18
- 238000004544 sputter deposition Methods 0.000 claims description 15
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- 239000000203 mixture Substances 0.000 description 5
- 230000005374 Kerr effect Effects 0.000 description 4
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- 229910052786 argon Inorganic materials 0.000 description 3
- 239000011651 chromium Substances 0.000 description 3
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910000808 amorphous metal alloy Inorganic materials 0.000 description 1
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Images
Classifications
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/62—Record carriers characterised by the selection of the material
- G11B5/64—Record carriers characterised by the selection of the material comprising only the magnetic material without bonding agent
- G11B5/65—Record carriers characterised by the selection of the material comprising only the magnetic material without bonding agent characterised by its composition
- G11B5/656—Record carriers characterised by the selection of the material comprising only the magnetic material without bonding agent characterised by its composition containing Co
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
- H01F10/00—Thin magnetic films, e.g. of one-domain structure
- H01F10/08—Thin magnetic films, e.g. of one-domain structure characterised by magnetic layers
- H01F10/10—Thin magnetic films, e.g. of one-domain structure characterised by magnetic layers characterised by the composition
- H01F10/12—Thin magnetic films, e.g. of one-domain structure characterised by magnetic layers characterised by the composition being metals or alloys
- H01F10/13—Amorphous metallic alloys, e.g. glassy metals
- H01F10/133—Amorphous metallic alloys, e.g. glassy metals containing rare earth metals
- H01F10/135—Amorphous metallic alloys, e.g. glassy metals containing rare earth metals containing transition metals
- H01F10/137—Amorphous metallic alloys, e.g. glassy metals containing rare earth metals containing transition metals containing cobalt
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S428/00—Stock material or miscellaneous articles
- Y10S428/922—Static electricity metal bleed-off metallic stock
- Y10S428/9265—Special properties
- Y10S428/928—Magnetic property
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/12—All metal or with adjacent metals
- Y10T428/12431—Foil or filament smaller than 6 mils
- Y10T428/12438—Composite
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/12—All metal or with adjacent metals
- Y10T428/12465—All metal or with adjacent metals having magnetic properties, or preformed fiber orientation coordinate with shape
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/12—All metal or with adjacent metals
- Y10T428/12493—Composite; i.e., plural, adjacent, spatially distinct metal components [e.g., layers, joint, etc.]
- Y10T428/12736—Al-base component
- Y10T428/1275—Next to Group VIII or IB metal-base component
Definitions
- the present invention relates to a magnetic film comprising an amorphous magnetic thin film having an easy magnetizing axis perpendicular to a plane of substrate, and the preparation thereof.
- the present invention relates to a perpendicular magnetization film comprising an amorphous magnetic thin film suitably used as a high density magnetic storage as so-called perpendicular magnetic storage, opto-magnetic storage, or the like.
- a cobalt thin film containing chromium of a little less than 20 atomic % has been investigated for a perpendicular magnetic storage.
- a thin film composed of an alloy of cobalt and chromium prepared by a sputtering method, and the like is known to be capable of recording high density-information and to be corrosive resistant.
- the maximum value of the perpendicular uniaxial anisotropy constant Ku of the above-mentioned alloy film of cobalt and chromium- is about 0.2 J/cm 3 (2x106 erg/cm 3 ).
- a relationship Ku-2 n Ms 2 >0 must be satisfied, wherein Ms indicates saturation magnetization.
- the maximum value of Ms of a perpendicular magnetization film of an alloy of cobalt and chromium is about 0:07 Tesla (700 gausses).
- an intensity of a detected signal is considered to be proportional to Ms.
- Ms an intensity of a detected signal
- An alloy of samarium and cobalt that is, a composite of SmCo S , constitutes a hexagonal crystal, where c-axis is a direction of easy magnetization, and the uniaxial magnetic anisotropy constant reaches to a level of 10 J/cm 3 (10 8 erg/cm 3 ).
- a large anisotropy is also expected.
- a large anisotropy of a magnetic thin film causes a large coercive force. Therefore, it realizes the stabilities of written information bits.
- the EP-A-16404 discloses a magnetization film comprising a not magnetic substrate as carrier and supported thereon a recording layer consisting of an Sm-Co-alloy and methods for preparation thereof.
- An object of the present invention is to provide a perpendicular magnetization film without any applying a bias voltage in its preparation process.
- the present invention relates to perpendicular magnetization film comprising an amorphous magnetic thin film of an alloy of samarium, cobalt and bismuth, having an easy magnetizing axis perpendicular to a plane of substrate, and further relates to the preparation of the above described film by depositing samarium, cobalt and bismuth onto the substrate.
- Fig. 1 is a graph of magnetization curves of a thin film of an alloy of samarium, cobalt and bismuth of the formula of (S M16 C O84 ) 62 Bi 38 .
- the continuous line indicates the magnetization along an easy magnetizing direction (perpendicular to the film), and the dashed line indicates the magnetization along a hard magnetizing direction (parallel to the film).
- a perpendicular magnetization film is prepared from an alloy of samarium, cobalt and bismuth.
- a content of bismuth of the alloy is preferably 0.1 to 40 atomic %, and more preferably 1 to 20 atomic %. When the content is less than 0.1 atomic %, the effect of adding bismuth is not practically recognized. An addition of bismuth more than 40 atomic % results in a reduction of saturation magnetization. And the deposited magnetic thin film is easily peeled off from the substrate.
- a proportion of samarium to the alloy is preferably 5 to 50 atomic %, and more preferably 10 to 40 atomic %.
- an anisotropy constant Ku of the alloy tends to become large.
- Ms also becomes large, so that Ku-2 n Ms 2 remains negative.
- Ku and Ms are decreased.
- a material having low Ku and Ms produces an unsuitable magnetic film as a data storage.
- a perpendicular magnetization film of the above described components in the invention is prepared on a substrate by sputtering, electron-beam-heating-evaporation, ion plating or the like.
- a substrate not only an aluminum plate or a glass plate but also a plastic plate or film injected from polymethylmethacrylate, polyimide, polycarbonate and the like can be readily used, as well.
- the substrate should be set substantially perpendicular to the incident direction of the metal vapour.
- a perpendicular magnetization film of samarium, cobalt and bismuth is provided on the substrate through the following sputtering processes.
- Target (cathod) of sputtering is optionally adopted singularly or plurally.
- a bismuth plate is set on the cathod or the backing plate.
- cobalt plate with many holes and samarium chips are put down respectively.
- the composition of the magnetic film is optionally controlled.
- the composition of the film can be controlled by choosing a power applied to every target.
- a target of an alloy of any compositions of samarium, cobalt or bismuth can be alternatively used.
- the homogeneity of the film is maintained by rotating the substrate above the target.
- Sputtering is performed under a pressure of 0,133 to 1,33 Pa (1 x10- 3 to 1 x 10- 2 Torr) of argon. With respect to an enlargement of the anisotropy, a lower pressure is more favorable.
- a substrate is not too much heated, e.g. 0°C to 200°C, and sputtering rate is not too fast, e.g. 1 nm to 1 pm (10 A to 10,000 A) per minute. Excepting the above stated matters, the sputtering conditions in the invention is not different from those in an ordinary sputtering.
- a thickness of the film is preferably 10 nm to 1 pm (100 A to 10,000 A).
- the thickness of the film is below 10 nm (100 A)
- a leakage flux is so small that a sensitivity for reading out the written informations is low.
- the thickness is more than 1 um (10,000 A)
- using a film of more than 1 ⁇ m (10,000 A) results in a waste of material.
- a protection layer of silicon, silicon oxide, silicon nitride, or the like can be provided onto a deposited film.
- the reason for providing the protection layer is that the film of the invention is weak to the oxidation since it includes samarium and cobalt.
- a magnetic film with a large perpendicular anistropy can be obtained by adding bismuth.
- bismuth When bismuth is not added, a perpendicular magnetization film cannot be obtained because a perpendicular uniaxial anisotropy constant Ku will be less than -0,1 J/cm 3 (-1 x10 6 erg/cm 3 ).
- Ku will be increased over 0,1 J/cm 3 (1x106 erg/cm 3 ) in proportion to the content of bismuth.
- large magnetic anisotropy constant is obtained when a concentration of samarium is small.
- the value of Ms is so large that Ku-2 ⁇ Ms 2 becomes negative, and a perpendicualr magnetization film is not obtained.
- a concentration of samarium is limited in a range of 5 to 50 atomic %.
- Adding bismuth results in a decrease of the saturation magnetization.
- the addition of bismuth is limited, too. This limit varies depending on a condition of deposition, e.g. bias voltage. The limit becomes low on applying a negative bias voltage to the substrate.
- a magnetic thin film obtained under the above-described condition has a coercive force of 23874 to 55706 A/m (300 to 700 Oe (oersteds)).
- the coercive force is measured in a perpendicular direction to the film by applying the magnetic field in the same direction.
- a bismuth-added magnetic thin film of samarium and cobalt can have a perpendicular anisotropy without any applying a bias voltage.
- a bias voltage is applied and at the same time bismuth is added
- a magnetic thin film with a larger perpendicular anisotropic constant Ku is obtained than when only bismuth is added.
- Ku becomes positive without adding bismuth.
- bismuth is added by 20 atomic %, Ku of as much as 0,6 J/cm 3 (6x10 6 erg/cm 3 ) is obtained. With this value of Ku, a perpendicular magnetization film of Ms of about 0.1 tesla (1000 gausses) can be obtained.
- an electro-magnetic interaction is employed for reading out an information magnetically stored in the media.
- a perpendicular magnetization film as provided in the present invention is used, "magnetic Kerr effect" can be also employed.
- Kerr effect When employing Kerr effect, a large Kerr rotation-angle is preferable since a sensitivity for reading out is proportional to the angle.
- An effect of adding bismuth is that the described Kerr rotation-angle is enhanced. For instance, a magnetic thin film of samarium and cobalt without bismuth has the Kerr rotation angle of 0.2°.
- the Kerr rotating angle reaches to 0.33°.
- an addition of bismuth of more than 10 atomic % causes a decrease of a Kerr rotation-angle.
- an addition of bismuth of about 15 atomic % is the most favorable from a viewpoint of increasing Kerr rotation-angle.
- a perpendicular magnetization film of an alloy of samarium, cobalt and bismuth in the invention is amorphous. This is verified by a X-ray diffraction measurement. This is a third distinctive feature of the invention.
- a grain boundary noise can be so small that reading out under a high signal-to-noise ratio is attained.
- the grain boundary noise is not negligible.
- the thin film of an alloy of samarium, cobalt and bismuth in the invention has a larger perpendicular magnetic anisotropy as compared with a film of an alloy of cobalt and samarium. Furthermore it provides an opto-magnetic storage with a large magnetic Kerr rotation-angle. As a result, it provides a high density magnetic storage capable of reading out easily.
- the target was, as usual, arranged at the bottom side and the substrate was arranged at the upper side in the face of the target. This arrangement was the so-called sputter-up type.
- a bismuth plate having a diameter of 8 cm was placed on the target backing plate, and thereon a cobalt plate of the same diameter perforated by many holes of a diameter of 6 mm was placed and samarium chips of 1 cm square were placed on the cobalt plate.
- a composition of the magnetic film was controlled by varying the number of holes and chips.
- a content of bismuth was proportional to the number of holes of cobalt plate.
- the sputtering condition was such that a pressure of argon was 0.266 Pa (2x10 -3 Torr), a sputtering rate was about 100 nm (1000 A) per minute, a bias voltage was not applied to the substrate, and the substrate was cooled with water.
- a bias voltage was not applied to the substrate, and the substrate was cooled with water.
- a coercive force Hc 1 perpendicular to the film plane was 15916 to 71622 A/m (200 to 900 Oe).
- the structure of the film was analyzed by means of X-ray diffraction. In any films, sharp peaks were not recognized, so that structures of the films were identified as amorphous.
- magnetron sputtering apparatus equipped with dual targets was used and a negative bias voltage was applied to the substrate.
- the sputtering powers applied to each targets were independently controlled.
- the substrate could rotate above the targets.
- One target was of a samarium plate on which cobalt sectors were placed.
- the other target was of bismuth only.
- the sputtering condition was such that the pressure of argon was 1,33 Pa (1 x 10- 2 Torr), the deposition rate was about 50 nm (500 A) per minute, the speed of rotation was 60 rpm, a bias voltage of -40 V was applied to the substrate and the substrate was cooled with water.
- Perpendicular magnetic anisotropy constants Ku of the obtained films were measured in the same manner as in Example 1. The results are shown in Table 2.
- Magnetic thin film was prepared under the same condition as in Example 9 except that a bismuth was not added.
- Ku was positive but smaller than those in Examples 9 to 11. The result is shown in Table 2.
- Magnetic thin films composed of samarium, cobalt and bismuth were prepared under the same condition as in Example 9.
- the polar Kerr effect was measured by means of Kerr effect hysterisis- measuring apparatus, where a light of He-Ne gas laser (the wave length was 633 nm) was used.
- the measured Kerr rotation-angles are shown in Table 3.
- Magnetic thin films were prepared under the same conditions as in Example 12 except that bismuth was not added.
- the Kerr rotation-angles of the films were smaller than those in Examples 12 to 15. The results are shown in Table 3.
- a magnetic film composed of samarium, cobalt and bismuth was prepared under the same condition as in Example 9 except that a bias voltage was not applied.
- a chemical formula of the obtained film was (Sm 16 C0 84 ) 62 Bi 38 , the thickness was 180 nm (1800 A) and the saturation magnetization was 4,1 . 10-2 t (410 Gausses).
- a perpendicular magnetic anisotropy constant was measured as 0.06 J/cm 3 (0.6x10 6 erg/cm 3 ) under external magnetic field of 1.35 - 10 6 A/m (17,000 Oe).
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- Chemical & Material Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Thin Magnetic Films (AREA)
- Magnetic Record Carriers (AREA)
Description
- The present invention relates to a magnetic film comprising an amorphous magnetic thin film having an easy magnetizing axis perpendicular to a plane of substrate, and the preparation thereof.
- Especially, the present invention relates to a perpendicular magnetization film comprising an amorphous magnetic thin film suitably used as a high density magnetic storage as so-called perpendicular magnetic storage, opto-magnetic storage, or the like.
- Hitherto, a cobalt thin film containing chromium of a little less than 20 atomic % has been investigated for a perpendicular magnetic storage. A thin film composed of an alloy of cobalt and chromium prepared by a sputtering method, and the like is known to be capable of recording high density-information and to be corrosive resistant.
- The maximum value of the perpendicular uniaxial anisotropy constant Ku of the above-mentioned alloy film of cobalt and chromium-is about 0.2 J/cm3 (2x106 erg/cm3). In order that an easy magnetizing direction is perpendicular to substrate, a relationship Ku-2 n Ms2>0 must be satisfied, wherein Ms indicates saturation magnetization. As a result, the maximum value of Ms of a perpendicular magnetization film of an alloy of cobalt and chromium is about 0:07 Tesla (700 gausses).
- For reading a stored information, an intensity of a detected signal is considered to be proportional to Ms. Thus, a larger Ms brings a favorable magnetic storage.
- An alloy of samarium and cobalt, that is, a composite of SmCoS, constitutes a hexagonal crystal, where c-axis is a direction of easy magnetization, and the uniaxial magnetic anisotropy constant reaches to a level of 10 J/cm3 (108 erg/cm3). In an amorphous alloy of samarium and cobalt, a large anisotropy is also expected. By turning an easy axis of the thin amorphous film to the perpendicular direction to the substrate, one can obtain a perpendicular magnetization thin film of large Ms. In addition, a large anisotropy of a magnetic thin film causes a large coercive force. Therefore, it realizes the stabilities of written information bits. The EP-A-16404 discloses a magnetization film comprising a not magnetic substrate as carrier and supported thereon a recording layer consisting of an Sm-Co-alloy and methods for preparation thereof.
- However, when a deposition of an alloy of samarium and cobalt is performed using an ordinary method such as electron-beam-evaporation or sputtering, the easy magnetizing direction is readily parallel to the substrate. Thus a perpendicular magnetization film cannot be obtained. Recently it is recognized that a perpendicular magnetization film can be prepared in sputtering by applying a negative bias voltage to the substrate. However, in that method, another circuit for supplying a voltage must be provided since a substrate is an insulator in most cases, so that the preparation process becomes complicated. More than anything else, a perpendicular magnetization film cannot be obtained by way of resistance heating- or electron beam heating-evaporation.
- An object of the present invention is to provide a perpendicular magnetization film without any applying a bias voltage in its preparation process.
- The present invention relates to perpendicular magnetization film comprising an amorphous magnetic thin film of an alloy of samarium, cobalt and bismuth, having an easy magnetizing axis perpendicular to a plane of substrate, and further relates to the preparation of the above described film by depositing samarium, cobalt and bismuth onto the substrate.
- Fig. 1 is a graph of magnetization curves of a thin film of an alloy of samarium, cobalt and bismuth of the formula of (SM16CO84)62Bi38. The continuous line indicates the magnetization along an easy magnetizing direction (perpendicular to the film), and the dashed line indicates the magnetization along a hard magnetizing direction (parallel to the film).
- In the present invention, a perpendicular magnetization film is prepared from an alloy of samarium, cobalt and bismuth. A content of bismuth of the alloy is preferably 0.1 to 40 atomic %, and more preferably 1 to 20 atomic %. When the content is less than 0.1 atomic %, the effect of adding bismuth is not practically recognized. An addition of bismuth more than 40 atomic % results in a reduction of saturation magnetization. And the deposited magnetic thin film is easily peeled off from the substrate.
- A proportion of samarium to the alloy is preferably 5 to 50 atomic %, and more preferably 10 to 40 atomic %. When a proportion of samarium is below 5 atomic %, an anisotropy constant Ku of the alloy tends to become large. However, Ms also becomes large, so that Ku-2 n Ms2 remains negative. As a result, a perpendicular magnetization film cannot be obtained. On the other hand, when a samarium is above 50 atomic %, both Ku and Ms are decreased. A material having low Ku and Ms produces an unsuitable magnetic film as a data storage.
- A perpendicular magnetization film of the above described components in the invention is prepared on a substrate by sputtering, electron-beam-heating-evaporation, ion plating or the like.
- For a substrate, not only an aluminum plate or a glass plate but also a plastic plate or film injected from polymethylmethacrylate, polyimide, polycarbonate and the like can be readily used, as well. The substrate should be set substantially perpendicular to the incident direction of the metal vapour.
- Thereafter, a perpendicular magnetization film of samarium, cobalt and bismuth is provided on the substrate through the following sputtering processes.
- In the present invention, a precise control of the contents of samarium, cobalt and bismuth is very important. Target (cathod) of sputtering is optionally adopted singularly or plurally. When single target is used, a bismuth plate is set on the cathod or the backing plate. On the bismuth plate, cobalt plate with many holes and samarium chips are put down respectively. By changing the number of the chips or holes, the composition of the magnetic film is optionally controlled. When plural targets are employed, the composition of the film can be controlled by choosing a power applied to every target. Furthermore a target of an alloy of any compositions of samarium, cobalt or bismuth can be alternatively used. In a single target type or plural target type of sputtering apparatus, the homogeneity of the film is maintained by rotating the substrate above the target.
- Sputtering is performed under a pressure of 0,133 to 1,33 Pa (1 x10-3 to 1 x 10-2 Torr) of argon. With respect to an enlargement of the anisotropy, a lower pressure is more favorable.
- Furthermore, for reducing the crystallization of the magnetic film, it is preferable that a substrate is not too much heated, e.g. 0°C to 200°C, and sputtering rate is not too fast, e.g. 1 nm to 1 pm (10 A to 10,000 A) per minute. Excepting the above stated matters, the sputtering conditions in the invention is not different from those in an ordinary sputtering.
- A thickness of the film is preferably 10 nm to 1 pm (100 A to 10,000 A). When the thickness of the film is below 10 nm (100 A), a leakage flux is so small that a sensitivity for reading out the written informations is low. On the other hand, when the thickness is more than 1 um (10,000 A), it will be difficult to write down the informations throughout the magnetic film. Thus, using a film of more than 1 µm (10,000 A) results in a waste of material.
- A protection layer of silicon, silicon oxide, silicon nitride, or the like can be provided onto a deposited film. The reason for providing the protection layer is that the film of the invention is weak to the oxidation since it includes samarium and cobalt.
- The perpendicular magnetization film of the invention has the following characteristics:
- First, a magnetic film with a large perpendicular anistropy can be obtained by adding bismuth. When bismuth is not added, a perpendicular magnetization film cannot be obtained because a perpendicular uniaxial anisotropy constant Ku will be less than -0,1 J/cm3 (-1 x106 erg/cm3). However, by adding bismuth, Ku will be increased over 0,1 J/cm3 (1x106 erg/cm3) in proportion to the content of bismuth. In general, large magnetic anisotropy constant is obtained when a concentration of samarium is small. However, in that case, the value of Ms is so large that Ku-2 π Ms2 becomes negative, and a perpendicualr magnetization film is not obtained. A concentration of samarium is limited in a range of 5 to 50 atomic %. Adding bismuth results in a decrease of the saturation magnetization. Moreover, when bismuth is added too much, the magnetic thin. film deposited on the substrate is easily peeled off. That is to say, the addition of bismuth is limited, too. This limit varies depending on a condition of deposition, e.g. bias voltage. The limit becomes low on applying a negative bias voltage to the substrate.
- A magnetic thin film obtained under the above-described condition has a coercive force of 23874 to 55706 A/m (300 to 700 Oe (oersteds)). The coercive force is measured in a perpendicular direction to the film by applying the magnetic field in the same direction.
- As described above, a bismuth-added magnetic thin film of samarium and cobalt can have a perpendicular anisotropy without any applying a bias voltage. However, when a bias voltage is applied and at the same time bismuth is added, a magnetic thin film with a larger perpendicular anisotropic constant Ku is obtained than when only bismuth is added. For instance, under applying a bias voltage of -40 V, Ku becomes positive without adding bismuth. However, when bismuth is added by 20 atomic %, Ku of as much as 0,6 J/cm3 (6x106 erg/cm3) is obtained. With this value of Ku, a perpendicular magnetization film of Ms of about 0.1 tesla (1000 gausses) can be obtained.
- Next, a second effect by adding bismuth is as follows:
- Usually, for reading out an information magnetically stored in the media, an electro-magnetic interaction is employed. However, when a perpendicular magnetization film as provided in the present invention is used, "magnetic Kerr effect" can be also employed. When employing Kerr effect, a large Kerr rotation-angle is preferable since a sensitivity for reading out is proportional to the angle. An effect of adding bismuth is that the described Kerr rotation-angle is enhanced. For instance, a magnetic thin film of samarium and cobalt without bismuth has the Kerr rotation angle of 0.2°. On the other hand, by adding bismuth till about 10 atomic %, the Kerr rotating angle reaches to 0.33°. However, an addition of bismuth of more than 10 atomic % causes a decrease of a Kerr rotation-angle. In conclusion, an addition of bismuth of about 15 atomic % is the most favorable from a viewpoint of increasing Kerr rotation-angle.
- A perpendicular magnetization film of an alloy of samarium, cobalt and bismuth in the invention is amorphous. This is verified by a X-ray diffraction measurement. This is a third distinctive feature of the invention.
- That is to say, concerning such an amorphous film as in the invention a grain boundary noise can be so small that reading out under a high signal-to-noise ratio is attained. In a polycrystalline opto-magnetic film, the grain boundary noise is not negligible.
- The thin film of an alloy of samarium, cobalt and bismuth in the invention has a larger perpendicular magnetic anisotropy as compared with a film of an alloy of cobalt and samarium. Furthermore it provides an opto-magnetic storage with a large magnetic Kerr rotation-angle. As a result, it provides a high density magnetic storage capable of reading out easily.
- A perpendicular magnetization film in the present invention and its preparation are experimentally explained by the following Examples. It is to be understood that the present invention is not limited to Examples, and various changes and modifications may be made in the invention without departing from the spirit and scope thereof.
- The following examinations were performed by using high frequency sputtering apparatus. The target was, as usual, arranged at the bottom side and the substrate was arranged at the upper side in the face of the target. This arrangement was the so-called sputter-up type. A bismuth plate having a diameter of 8 cm was placed on the target backing plate, and thereon a cobalt plate of the same diameter perforated by many holes of a diameter of 6 mm was placed and samarium chips of 1 cm square were placed on the cobalt plate.
- A composition of the magnetic film was controlled by varying the number of holes and chips. A content of bismuth was proportional to the number of holes of cobalt plate.
- Glasses of 1 mm thickness were used as substrates. The sputtering condition was such that a pressure of argon was 0.266 Pa (2x10-3 Torr), a sputtering rate was about 100 nm (1000 A) per minute, a bias voltage was not applied to the substrate, and the substrate was cooled with water. In the above-described conditions, magnetic thin films of various compositions were prepared.
- Uniaxial magnetic anisotropy constant K1 perpendicular to the substrate was measured by a torque meter. The saturation magnetization Ms was measured by means of vibrating sample magnetometer. The perpendicular magnetic anisotropy constant Ku was obtained from the relationship Ku=K⊥+2π Ms2. The results are shown in Table 1.
- A coercive force Hc1 perpendicular to the film plane was 15916 to 71622 A/m (200 to 900 Oe).
- The structure of the film was analyzed by means of X-ray diffraction. In any films, sharp peaks were not recognized, so that structures of the films were identified as amorphous.
- Magnetic thin films were prepared in the same manner as Example 1 except that the cobalt plate had no holes. In all cases, Ku's were below zero. The results are shown in Table 1.
- In these examples, magnetron sputtering apparatus equipped with dual targets was used and a negative bias voltage was applied to the substrate. The sputtering powers applied to each targets were independently controlled. The substrate could rotate above the targets. One target was of a samarium plate on which cobalt sectors were placed. The other target was of bismuth only. The sputtering condition was such that the pressure of argon was 1,33 Pa (1 x 10-2 Torr), the deposition rate was about 50 nm (500 A) per minute, the speed of rotation was 60 rpm, a bias voltage of -40 V was applied to the substrate and the substrate was cooled with water. Perpendicular magnetic anisotropy constants Ku of the obtained films were measured in the same manner as in Example 1. The results are shown in Table 2.
- Magnetic thin film was prepared under the same condition as in Example 9 except that a bismuth was not added. Ku was positive but smaller than those in Examples 9 to 11. The result is shown in Table 2.
- Magnetic thin films composed of samarium, cobalt and bismuth were prepared under the same condition as in Example 9. The polar Kerr effect was measured by means of Kerr effect hysterisis- measuring apparatus, where a light of He-Ne gas laser (the wave length was 633 nm) was used. The measured Kerr rotation-angles are shown in Table 3.
- Magnetic thin films were prepared under the same conditions as in Example 12 except that bismuth was not added. The Kerr rotation-angles of the films were smaller than those in Examples 12 to 15. The results are shown in Table 3.
- A magnetic film composed of samarium, cobalt and bismuth was prepared under the same condition as in Example 9 except that a bias voltage was not applied.
- A chemical formula of the obtained film was (Sm16C084)62Bi38, the thickness was 180 nm (1800 A) and the saturation magnetization was 4,1 . 10-2 t (410 Gausses). A perpendicular magnetic anisotropy constant was measured as 0.06 J/cm3 (0.6x106 erg/cm3) under external magnetic field of 1.35 - 106 A/m (17,000 Oe). A modified Ku=Ki+2 n Ms2 was 0.166 J/cm3 (1.66x 10s erg/cm3). Magnetization curves in both directions perpendicular and parallel to the film plane were shown in Fig. 1.
Claims (4)
Applications Claiming Priority (2)
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JP120391/84 | 1984-06-12 | ||
JP59120391A JPS61544A (en) | 1984-06-12 | 1984-06-12 | Vertically magnetizable film |
Publications (3)
Publication Number | Publication Date |
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EP0164725A2 EP0164725A2 (en) | 1985-12-18 |
EP0164725A3 EP0164725A3 (en) | 1986-12-30 |
EP0164725B1 true EP0164725B1 (en) | 1989-09-27 |
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Application Number | Title | Priority Date | Filing Date |
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EP85107164A Expired EP0164725B1 (en) | 1984-06-12 | 1985-06-11 | Perpendicular magnetization film and its production |
Country Status (4)
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US (1) | US4675239A (en) |
EP (1) | EP0164725B1 (en) |
JP (1) | JPS61544A (en) |
DE (1) | DE3573352D1 (en) |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
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US4597573A (en) * | 1985-02-07 | 1986-07-01 | Crown Zellerbach Corporation | System for handling discrete sheets |
JPS6326827A (en) * | 1986-07-21 | 1988-02-04 | Hitachi Ltd | Production of magnetic recording medium |
JP2819292B2 (en) * | 1988-05-31 | 1998-10-30 | ファーネス重工株式会社 | Furnace |
JP3090128B2 (en) * | 1998-08-28 | 2000-09-18 | 日本電気株式会社 | Perpendicular magnetic recording media |
KR100341843B1 (en) * | 2000-04-12 | 2002-06-24 | 황정남 | Rotation of Magnetic Easy-Axis and Multiple Easy-Axis in Magnetic Materials and the Fabrication Method of the Same |
KR100598578B1 (en) * | 2004-11-25 | 2006-07-13 | 한국전자통신연구원 | Method of manufacturing a form factor disk |
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US4126494A (en) * | 1975-10-20 | 1978-11-21 | Kokusai Denshin Denwa Kabushiki Kaisha | Magnetic transfer record film |
JPS53104897A (en) * | 1977-02-25 | 1978-09-12 | Toshiba Corp | Magnetic head |
DE2909891A1 (en) * | 1979-03-14 | 1980-09-25 | Basf Ag | MAGNETIC RECORDING CARRIER |
DE2911992C2 (en) * | 1979-03-27 | 1981-12-10 | Philips Patentverwaltung Gmbh, 2000 Hamburg | Magneto-optic memory element, process for its manufacture and memory device using it |
JPH06104870B2 (en) * | 1981-08-11 | 1994-12-21 | 株式会社日立製作所 | Method for producing amorphous thin film |
JPS5967612A (en) * | 1982-10-09 | 1984-04-17 | Yoshifumi Sakurai | Manufacture of photomagnetic recording medium |
US4469536A (en) * | 1982-11-10 | 1984-09-04 | The United States Of America As Represented By The Secretary Of The Navy | Alloys and method of making |
JPS59208706A (en) * | 1983-05-12 | 1984-11-27 | Daido Steel Co Ltd | Thermomagnetic recording material |
-
1984
- 1984-06-12 JP JP59120391A patent/JPS61544A/en active Granted
-
1985
- 1985-06-10 US US06/743,134 patent/US4675239A/en not_active Expired - Fee Related
- 1985-06-11 EP EP85107164A patent/EP0164725B1/en not_active Expired
- 1985-06-11 DE DE8585107164T patent/DE3573352D1/en not_active Expired
Also Published As
Publication number | Publication date |
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DE3573352D1 (en) | 1989-11-02 |
EP0164725A2 (en) | 1985-12-18 |
US4675239A (en) | 1987-06-23 |
EP0164725A3 (en) | 1986-12-30 |
JPS61544A (en) | 1986-01-06 |
JPH0418023B2 (en) | 1992-03-26 |
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